Chemistry Reference
In-Depth Information
1993, 1996). MJLCP distinguishes itself from other main classes of liquid
crystal polymers (Figure 3.1) by having chemical structures similar to con-
ventional side-group type liquid crystalline polymers but chain properties
similar to rigid or semi-rigid main-chain type liquid crystalline polymers.
Shown below are a few examples of the molecular design of MJLCPs:
Poly-2,5-bis[(4-R-substituted)benzoyloxy]styrene:
~
~
CH
2
C
H
OOC
R
R
COO
PE-R
Poly-2,5-bis[(4-R-substituted)benzamido]styrene:
~
~
CH
2
C
H
NH
C
O
R
R
C
O
NH
PA-R
Poly-3-vinyl-
{
2,6-bis(4-R-substituted)phenyl
}
benzo-[1,2-d;4,5-d']bisthi-
azole:
~
~
CH
2
C
H
S
N
C
R
C
R
N
S
PBTA-R
Other
designs
are
possible.
Among
the
above
three
polymers,
PE-R
and
PA-R
are the most studied while
PBTA-R
is still
to be synthesized (Zhou
et al
.,
1987;
1989;
1993;
1996).
Poly-2,5-
bis[(4-R-substituted)benzoyloxy]styrenes,
PE-R
, and Poly-2,5-bis[(4-R-
substituted)benzamido]styrene,
have been synthesized by radical
chain polymerizations of corresponding monomers. Table 3.14 shows some
of the characterization results for some of the
PA-R
polymers.
Although the mesogenic substituent on the vinyl group is bulky and
rigid, high molecular weights have been achieved in the syntheses. For the
high polymerizability of these monomers, we have the following plausi-
ble explanation: the nematic interaction among monomer molecules has
brought vinyl groups close to a favorable position relative to each other. As
reference, for a single crystal of a few of the monomers, WAXS has revealed
PE-R
